Study On Effective Substance Of Yeast Culture Regulating Rumen Function Of Sheep

Yeast culture（YC）showed obvious growth-promoting effects.Due to the complex composition of YC,the functional substances in yeast culture affecting rumen fermentation are not clear,leading to the function is not clear,which limits the application of YC to a certain extent.The study aimed to preliminarily determine the effective metabolite composition of YC by exploring the effect of YC on rumen fermentation in vitro and the growth performance of sheep.This experiment provided a theoretical basis for optimizing the technology of YC quickly and efficiently and explored the mechanism of YC,which is of great significance for clarifying the mechanism of nutrition and health care of YC.Experiment 1:Screening of effective substances for regulating rumen function of sheep in yeast culture.This chapter explored the effect of different yeast cultures on rumen fermentation of sheep in vitro.The different yeast cultures can provide materials for searching the effective substances in yeast cultures.A single regression equation was established between MFAEI and yeast culture components which had a positive effect on rumen fermentation.And the effective substances in yeast culture that positively regulated rumen fermentation were preliminarily determined.Four different yeast cultures（product A,product B,product C,and product D）were prepared during production.A single factor experiment design was used and the experiment was divided into 5treatment groups with 5 replicates in each group.The control group（without any additives）and the four different yeast culture groups（group A,group B,group C,and group D）.Rumen fermentation parameters were determined after fermentation on 3,6,12,and 24h in vitro.The results showed that different YC products had no significant effect on p H and dry matter degradation rate at different times of rumen fermentation in vitro（P>0.05）,however,compared with the control group,the dry matter degradation rate of groups A,B,C and D increased by 4.5%,7.66%,6.73%and3.41%,respectively.The concentration of NH₃-N in groups A and D was significantly higher than that of the control group on 3h and 24h of rumen fermentation in vitro.The concentration of MCP in groups B and C was significantly higher than that in the control group on 6h of rumen fermentation in vitro（P<0.05）.The total VFA concentration in group A and group B was significantly higher than that of the control group for 3h（P<0.05）,and there was no significant difference among other groups of rumen fermentation in vitro（P>0.05）.The total VFA concentration in group B was significantly higher when compared with the control group on 6h of rumen fermentation in vitro（P<0.05）.There was no significant difference in total VFA among all groups on 12 and 24h of rumen fermentation in vitro（P>0.05）.According to the range and standard error among different groups,the variation degree of MFAEI on 6h was greater than that on 3h,12h and,24h of rumen fermentation in vitro.According to Pearson correlation results,the effective substances in YC promoting rumen fermentation were determined to be Propanoic acid,Oxalic acid,D-Lyxose,5-Hydroxytryptophan,3-A-Mannobiose,and D-（+）-Turanose.The best unary regression model y=f（x_i）was established between the main effective substances（x）in YC and the MFAEI value（y）on 6h of rumen fermentation,respectively.The regression equation with the highest R² after fitting and P<0.05 was selected as the final equation of each metabolite and MFAEI.According to y=max,calculate x value,That is,when MFAEI is at its maximum,the optimal dose of the 6effective substances in YC were determined as:x₁=0.77%,x₂₌0.66%,x₃₌0.82%,x₄₌0.40%,x₅₌0.63%and x₆₌3.36%.In addition,according to the MFAEI of different groups on 6h of rumen fermentation,group B was determined to have the greatest influence on rumen fermentation,and product B was selected for subsequent tests.Experiment 2:Validation of effective substances in yeast culture regulating rumen function of sheep in vitro.This chapter aims to determine whether the combination product had a positive effect on rumen fermentation through the effects of different doses of the combination product on rumen fermentation in vitro,so as to verify the effectiveness of the combination product.A single factor experimental design was adopted,and the experiment was divided into 5 groups with 5 replicates in each group,namely,the control group without any additives,the YC group（0.625‰of product B）,and three combination groups with different levels of combination product（0.005‰,0.025‰,0.05‰）.The rumen fermentation parameters and the diversity and metabolite groups of rumen microflora were determined after 6h in vitro culture.The functional substance is prepared with a pure chemical product and the combined ratio was:Propanoic acid:Oxalic acid:D-Lyxose:5-hydroxytryptophan:3-A-Mannobiose:D-（+）-Turanose=9.90:11.56:12.34:5.97:9.52:50.71.The results showed that the NH3-N concentration in the YC group was significantly higher than that in other groups（P<0.05）.The concentration of MCP in combination groupⅠwas significantly higher when compared with the control group（P<0.05）.Compared with the control group,the concentrations of acetic acid and propionic acid in the combination groupⅢwere significantly increased（P<0.05）,while the concentrations of acetic acid and propionic acid in other groups showed no significant difference（P>0.05）.And the concentration of isobutyric acid in combination groupsⅡandⅢwere significantly higher（P<0.05）.Compared with the control group,YC and the combination product increased the concentration of total VFA,and the concentration of total VFA in combination groupsⅠandⅢwere significantly higher（P<0.05）.According to the MFAEI,with the increase of the combination product,the influence on rumen fermentation gradually increased,namely,combination groupⅢ>combination groupⅡ>combination groupⅠ.The Faith＿pd index in the YC group and combination group was significantly lower than that in control group of rumen fermentation in vitro,and the relative abundance of phylum Bacteroidetes in YC group and combination group was higher than that in the control group（P<0.05）,however phyla Firmicutes,Synergistetes,TM7 and Firmicutes/Bacteroidetes in the control group were significantly lower than those in the YC group and combination group（P<0.05）.The metabolism of microorganisms was significantly changed in YC group and combination group,and the concentrations of Adenosine,Methylmalonic acid,and Methylsuccinic acid in rumen fermentation fluid were significantly increased in rumen fermentation in vitro（P<0.05）.Experiment 3:Effects of effective substances in yeast culture regulating rumen function on growth performance,blood indices,rumen fermentation and metabolomics of sheepAn animal experiment was carried out to explore the effects of YC and combination products on growth performance,nutrient digestibility,blood indices,rumen microbial and metabolite groups of sheep,and further verify the efficacy of combination products.A total of thirty healthy sheep were selected and randomly divided into 3 treatment groups according to the principle of body weight,namely the control group,YC group（add a dose of 0.625‰）and pure combination group（add a dose of 0.037‰）with 10 replicates in each group and one sheep in each replicate.The experiment lasted for 60 days.Growth performance,slaughter performance,blood indices,rumen microbial,and metabolomics of sheep were determined.Compared with the control group,ADG in the YC group and combination group increased by8.15%（P>0.05）.The combination group significantly increased the slaughter rate and decreased the GR value of sheep（P<0.05）.The average daily intake of dry matter in the YC group and combination group showed an increasing trend and increased by2.85%and 7.40%when compared with the control group,respectively.The average daily intake of crude protein in the YC group and combination group was higher than that in the control group（P=0.066）.The average daily intake of fat in the combination group was higher than that in the control group and YC group（P<0.05）.The YC and combination groups absorbed 59g and 36g more starch per day than the control group,respectively（P=0.055）.On day 30,the level of growth hormone（GH）,cortisol,and insulin（INS）in serum in the combination group was significantly higher than in other groups（P<0.05）.On day 60,the level of GH in serum in the YC group and combination group were significantly higher than that in the control group（P<0.05）,and the level of cortisol and INS in the combination group were significantly higher than that in the control group（P<0.05）.And there was no significant difference in leptin（LEP）concentration among the groups（P>0.05）.When compared with the control group,the rumen VFA concentration in YC and combination group was increased,and the combination group was significantly higher（P<0.05）.The YC group increased the abundance of phylum Bacteroidetes in the rumen,however,the combination group decreased the abundance of phylum Bacteroidetes and increased the ratio of Firmicutes/Bacteroidetes in the rumen.Compared with the control group,the increased differential metabolites in both YC and the combination group were as follows:L-Glutamic acid,Silanol,Stearic acid,Palmitic Acid,Lactic Acid,L-Aspartic acid,Benzeneacetic acid,L-Alanine,2-Methylbutanoic acid,Uracil,Hexanoic acid,and purine.YC and the combination product increased the accumulation of rumen metabolites in amino acid metabolism and carbohydrate metabolism pathways.In the current study,rumen fermentation in vitro and animal tests were carried out.And the research preliminarily confirmed that the YC and effective substances had a positive effect on animal growth performance,slaughter performance,rumen fermentation,and microbial metabolic activities.